The oil industry has faced important changes in recent years. The production of light crude oil has decreased around the world, while the production of heavy and extra-heavy crude oils has been increasing. This situation has brought several drawbacks in the production, transportation, storage and refining of such crude oils.
Because of their properties of high specific gravity and high viscosity, heavy and extra-heavy crude oils require the application of different procedures and technologies to allow maintaining their fluidity and thereby be able to be transported from the production facilities to the distribution and refining centers, which are typically located hundreds of kilometers away.
The American Petroleum Institute classifies petroleum as “heavy” and “extra-heavy” according to the gravity API:                Heavy crude oils: have API gravities between 10 and 22.3°API; and        Extra-heavy crude oils: have API gravities less than 10°API.        
The most important property that defines if a heavy or extra-heavy crude oil can be transported by pipeline or not is the viscosity. The most common specification is a maximum value of kinematic viscosity of 250 centistokes (c t) at 37.8° C. (100° F.). API gravity is also used to determine the transportability of a heavy or extra-heavy crude oil, however, depending on the origin and nature of the crude oil, the API gravity value to ensure its transportation by pipeline ranges between 16-20°API minimum.
The procedures and technologies used for transporting the extra-heavy and heavy crude oils by pipeline can be classified into two groups: (1) viscosity reduction of heavy crude oils, and (2) reduction of friction of hydrocarbon within the pipeline. To upgrade the transport properties of heavy and extra-heavy crude oils, particularly the viscosity reduction, which is the main objective of this invention, the following methods are considered: (1) heating, (2) dilution, and (3) formation of emulsions, and (4) partial upgrading. Different procedures and technologies can be applied in each method.
Heating has a major effect on the viscosity of heavy crude oils and extra-heavy but it is difficult to carry out at practical level, consequently dilution methods have been the most used, however large amounts of solvents are required, which normally have a high cost. These procedures have a number of technological and economic limitations therefore their application is limited with the objective of not increasing the production costs of heavy crude oils.
The alternative of partial upgrading of the properties of heavy crude oils is a viable option in order to the transportation be possible in conventional production facilities to from a ground or maritime production center to the distribution and refining centers.
In order to maintain the profitability in the production of heavy crude oil, the upgrading process must satisfy certain characteristics: (1) it must be located near the centers of production, (2) it must need low amounts of catalyst, (3) it must use cheap catalyst and easy to obtain utilities in production center, (4) it must not generate large quantities of by-products that they require further processing, (5) it has to be of high capacity, but of small size.
The most related state-of-the-art to this invention by referring to the use of processes that combine several steps and/or refining steps (combined processes) to upgrade the properties of heavy and extra-heavy crude oils are represented by the following documents:
U.S. Pat. No. 4,485,004 (1984) protects a dispersed-phase hydrocracking process that operates at temperatures between 400 and 450° C., pressures between 110 and 170 Kg/cm2 and residence times between 2 and 3.5 hours. It uses dispersed catalysts based on cobalt, molybdenum, nickel and tungsten in concentrations between 3 and 5% respect to the feed. The hydrocracking catalyst may be fresh or spent and is diluted in a hydrogen donor hydrocarbon. The catalyst is composed of one or more of the following elements: Co, Mo, Ni, W and mixtures thereof. The used types of hydrogen donor include hydrocarbons such as tetralin or others with the ability of transferring hydrogen atoms to the thermally cracked fractions for example refinery streams such as cycle oils with boiling point about 200° C. The hydrocracked product is separated into different fractions according to their boiling point. The catalyst can be used in powder form with particle sizes between 425 μm and 45 μm (40 and 325 meshes according to ASTM E 11-87 method). The catalyst concentration can be from 3% to 5% and is fed together with the hydrocarbon. A portion of the recovered fraction that contain the catalyst in liquid phase is recirculated to the reactor.
U.S. Pat. No. 5,626,742 (1995) describes a continuous process for in situ upgrading of heavy crude oils using aqueous base (NaOH). It uses a temperature between 380 and 450° C. The main objective of this process is the upgrading through sulfur removal associated to organic molecules.
U.S. Pat. No. 8,062,503 (2007) protects a thermal upgrading process of heavy crude oils and residues using a pyrolysis reactor with a short residence time. The upflow stream of hydrocarbon is passed through a solid support (calcium oxide) where hydrocracking reactions occur. The operating temperature of this pyrolysis reactor is between 300 and 700° C. with a contact time between the hydrocarbon and the solid of less than 5 seconds.
U.S. Pat. No. 7,381,320 (2008) protects a type of even more complex applications that includes several processes of different nature as the separation of the heavy fractions by solvent extraction, fluid catalytic cracking and hydrocracking of heavy crude oil, as well as the effluent treatment plants for the used processes. Finally, it includes the formulation of the upgraded oil.
U.S. Pat. No. 7,449,103 (2006) claims the use of catalysts in colloidal or molecular phase in an ebullated bed reactor. The soluble catalyst is diluted in a hydrocarbon (vacuum gas oil, decanted oil, cycle oil or light gas oil) before its addition to the reactor. The reactor system can employ a homogeneous phase reactor and after an upstream ebullated bed reactor with larger catalyst particles. The catalyst used is molybdenum 2-ethylhexanoate with about 15 weight % Mo and with particle sizes less than 0.001 μm.
U.S. Patent application No. 20100200463 A1 describes a hydroconversion process at high severity using a molybdenum catalyst in dispersed phase in an array of at least two reactors in series. Operating temperature and pressure for this process are 400-480° C. and 200 Kg/cm2 respectively.
U.S. Patent application No. 20110155639 describes a process for producing synthetic crude oil that can be transportable by pipeline. It involves obtaining the heavy fraction of this crude oil (vacuum residue) which is subsequently subjected to a hydroconversion process in an ebullated bed reactor. The operating conditions no used in this reactor are the following: pressure of between 105 to 210 Kg/cm2, temperature between 400 to 450° C., hydrogen/hydrocarbon ratio between 1.500 to 10.000 ft3/bbl, space velocity of 0.1 to 1.5 hr−1 and a daily replenishment of catalyst 0.1 to 1.0 lb/bbl of feed. Several steps are involved: feeding heavy oil to a fractionation tower to obtain a light fraction and a heavy fraction, recovery by distillation of a vacuum residue, feeding of the vacuum residue together with hydrogen to a reaction system of ebullated bed type, and finally the hydroconverted residue is mixed with the light fraction for the preparation of an upgraded crude oil.
U.S. Patent Application No. A1 20110163004 proposes a system based on the creation of high pressure pulses on hot heavy crude oil in order to crack it and produce a crude oil with a lower viscosity.
U.S. Patent Application No. US 20120270957 A1 describes a process for reducing the viscosity and the contents of sulfur, metals and asphaltenes in bitumen. The process involves a number of well-known treatments such as: Fischer-Tropsch process for hydrogen generation, a hydrogenation reactor, and another upgrading operations and separation of hydrocarbons processes.
Regarding to the used catalyst in such processes, several patents describe a large number of materials used to upgrade the different hydrocarbon cuts. They are based mainly on the catalytic properties of heavy metals such as Mo, Ni, Co, Ti, W, and combinations with other elements such as C, O, S, P, etc. These elements are involved in the reactions of hydrocracking, hydrogen adsorption, and C—S bond breaking which together upgrade the properties of various cuts of hydrocarbons, from gasoline to heavy crudes oils and residues. Supports or refractory oxide based Al, Si, Ti, among others are other important elements of composition of these catalysts. Such supports can be amorphous or crystalline, such as zeolites and they give different properties of acidity or basicity to the catalyst.
U.S. Patent Application No. 20090011931 A1 explains the preparation and use of a catalyst which involves the utilization of a Group VIB metal oxide (MoO3) together with an aqueous ammonia solution. H2S addition steps are included (necessary to sulfidation of the metal oxide) and hydrogen. This mixture is combined with the heavy hydrocarbon at operating conditions that maintain the catalyst in solution.
Mexican Application Patents with file numbers MX/a/2010/013890 and MX/a/2010/013835 employ catalysts of iron oxide and alumina between 0.1 and 4 wt. %. These patents also describe good results using bauxite. This process operates at pressures in the range of 100 to 170 Kg/cm2, temperature between 440-465° C. and LHSV from 0.1 to 3 hr−1 using tubular reactors with upflow or downflow.
From the state-of-the-art described above known by the applicants, none of them describe a dispersed-phase hydrocracking process at low severity conditions using disposable low-cost catalysts, whose objective is the upgrading of the transport properties of extra-heavy and heavy crude oils.
It is therefore the purpose of this invention to provide an upgrading process that comprises the catalytic hydroconversion of heavy and/or extra-heavy crude oils using a disposable and low-cost catalyst.
The aim of the process and catalyst is to upgrade the transport properties of heavy and extra-heavy crude oils to be transported in production facilities and to distribution and refining centers.
An additional objective of this invention is to provide a process with low operating and investment costs that can be installed in the production centers of crude oils either on ground or offshore.
The severity of the process is limited to upgrade the transport properties of the heavy crude oil that is obtained from the production centers.
Although the diagram of FIG. 1 illustrates the specific provisions of equipment whereby this invention can be practically applied, it should not be to understand that this limits the invention to some specific equipment.